This invention concerns an apparatus to transport and cool rod, metal wires, steel round pieces or similar, in the segment between a coil-forming machine, arranged downstream of the last rolling stand of a rolling mill, and a collection device where the cooled product is wound into rolls or coils.
In the field of hot rolling mills, the state of the art includes apparatus to convey and simultaneously cool rolled product, such as rods, wires, bars, round pieces or similar, between the outlet of the last rolling stand and the collection device. The rolled product, in fact, which at outlet from the last rolling stand has a temperature of between 750xc2x0 C. and 1150xc2x0 C., before being wound into rolls or coils is properly cooled, and possibly subjected to heat treatment, to give it the desired final structure and the desired mechanical properties.
This cooling is usually achieved by using air, which is blown onto the product passing through by blowers arranged below a horizontal conveyor with rollers.
The rolled product, downstream from the last rolling stand, passes into a coil-forming head.
Since the density of the coils is higher in the lateral zone of the conveyor than in the central zone, it is necessary to provide means which provide a substantially uniform cooling of the product.
The state of the art includes an apparatus wherein, between the blowers which blow the air and the conveyor rollers there are one or more horizontal plates with differentiated apertures, consisting of slits or holes, to direct a greater quantity of air in correspondence with the lateral zones of the conveyor.
This conventional apparatus has the disadvantage, however, that it is very bulky, complex and therefore costly, and it is not versatile, because once the holed plates have been sized, and located between the blowers and the rollers, they are difficult to modify or replace with others having a different configuration of the apertures. This disadvantage is not insignificant, if we think that it is essential to adapt the cooling methods according to the type of product treated and the final result to be obtained. It must not be forgotten that the cooling curve of the product, that is, the progressive lowering of the temperature, univocally causes the phase transformation, and consequently the final mechanical characteristics of the product.
Document JP-A-59-113918 discloses a device to transport and cool rolled bars wound in coils, which comprises a plurality of conveyor rolls arranged with the axes of rotation parallel to each other. Each conveyor roll has a cylindrical central part, which has a set diameter and is able to contact the rolled stock to be conveyed, and two lateral parts with a smaller diameter than that of the central part. Between the rolls, brought into reciprocal proximity, passages are created for the cooling air, which is blown from below. The passages are narrower at the center and wider in correspondence with the lateral zones. The device has at least the following two disadvantages, however: the lateral ends of the conveyor rolls are weakened, since their diameter is reduced with respect to that of the central part; moreover, in correspondence with the lateral ends the coils tend to deform, because they have nothing to support them.
The present Applicant has devised, embodied and tested, with excellent results, the apparatus to transport and cool rolled products such as rods, wires, round pieces or similar according to the invention, to overcome these shortcomings of the state of the art.
The apparatus to transport and cool rolled products according to the invention is set forth and characterized in the main claim, while the dependent claims describe other innovative features of the invention.
The apparatus according to the invention, which is able to be arranged downstream of a coil-forming head in a rolling mill, comprises transport rollers, at least some of which are motorized, arranged parallel so as to define a substantially horizontal transport plane on which the rolled product arranged in coils is able to lie, ventilation means being arranged in correspondence with the transport rollers to blow air towards the rolled product and conveyor means to convey a greater quantity of air towards the lateral edges of the coils than that conveyed towards the central zone of the coils.
One purpose of the invention is to achieve means to convey the air which allow to cool the rolled product homogeneously while it is being transported by the transport rollers and which are at the same time simple, reliable and easy to replace.
In accordance with this purpose, the means to convey the air comprise a plurality of elements arranged at intervals between the transport rollers and shaped so as to define transit channels, or outflow gaps, having at least a first transverse section which is greater in correspondence with the ends of the transport rollers and at least a second transverse section which is less in correspondence with the median zone of the transport rollers.
The intermediate elements preferably consist of rollers arranged slightly lower than the drawing rollers, so that they do not interfere with the rolled product above, so they are so-called xe2x80x9cdummy rollersxe2x80x9d.
While the general concept applies that the diameter of the intermediate rollers is variable, the shape of the latter can be chosen as desired, according to the characteristics of the product to be cooled, the density of the coils, the speed of transport of the product and any other parameter which might influence the cooling curve.
According to another characteristic feature, which adds to and integrates the advantages of the intermediate elements, in the median zone of the conveyor conduit of the ventilation means two switches are provided; the controlled inclination thereof allows to direct more or less air towards the ends of both the drawing and the intermediate rollers.